> In the approach to woman as the spoil and hand-maid of communal lust
> is expressed the infinite degradation in which man exists for himself,
> for the secret of this approach has its unambiguous, decisive, plain
> and undisguised expression in the relation of man to woman and in the
> manner in which the direct and natural species-relationship is
> conceived. The direct, natural, and necessary relation of person to
> person is the relation of man to woman. In this natural
> species-relationship man's relation to nature is immediately his
> relation to man, just as his relation to man is immediately his
> relation to nature — his own natural destination. In this
> relationship, therefore, is sensuously manifested, reduced to an
> observable fact, the extent to which the human essence has become
> nature to man, or to which nature to him has become the human essence
> of man.
>
> From this relationship one can therefore judge man's whole level of
> development. From the character of this relationship follows how much
> man as a species-being, as man, has come to be himself and to
> comprehend himself; the relation of man to woman is the most natural
> relation of human being to human being. It therefore reveals the
> extent to which man's natural behaviour has become human, or the
> extent to which the human essence in him has become a natural essence
> — the extent to which his human nature has come to be natural to him.
> This relationship also reveals the extent to which man's need has
> become a human need; the extent to which, therefore, the other person
> as a person has become for him a need — the extent to which he in his
> individual existence is at the same time a social being.
>
> <http://www.marxists.org/archive/marx/works/1844/manuscripts/comm.htm>